A polyolefin which has an excessively high content of heptane-solubles may have a tendency to stick and is therefore difficult to convey and, as a result, is not very suitable for industrial applications. In addition, in the alimentary field, the presence of solubles in a polyolefin which is intended to come into contact with foodstuffs is deemed to be undesirable. For these reasons, for example, isotactic polypropylene preferably has a heptane-insolubles content (denoted by HI, from the expression "heptane-insoluble") higher than 80% by weight.
Patent application EP 250229 teaches that the use of certain silanes during the polymerization of olefins allows the hexane-solubles content of the polyolefin obtained to be reduced.
The paper by R. West, Journal of the American Chemical Society (1954) 76, 6012, describes a method for the preparation of 1,1-dimethoxysilacyclohexane. This preparation involves numerous stages and the intermediate formation of a chlorosilacycloalkane which is particularly tricky to handle and easily degradable.